Not a plumber... But plumbed my house 13 years ago when we moved in, and did all the sparks work. As a mechanic, you need to know good plumbing and elec practice to succeed!!! A bit of a Jack of all trades. Don't worry, I got all my work, checked and certified by qualified chaps!
Can you post a picture of your radiator and your boiler/pump and describe your house (ie, 3 bed semi 1200 sq foot etc) and I'll give you the benefit of my limited knowledge!